The need for treatment of unpaved roads and other outdoor surfaces to reduce airborne dust is well recognized. In addition to reduced driver visibility and adverse health and aesthetic consequences, airborne dust indicates deterioration and actual loss of road surface. This represents a significant cost in the form of loss of aggregate and increased maintenance time. Much of the need for dust control is on rural, unpaved aggregate roads, but dust control is important in many other areas, such as construction sites, mines, farms, golf courses, parking lots and so forth.
The prior art has provided numerous dust control agents to address these problems. The simplest way to reduce the release of airborne dust is to apply water. Water alone is a poor dust control agent, because its high surface tension decreases its efficiency in coating fine particles, and its rapid evaporation provides a very short useful life. Salt brines also may be used. Certain salts are hygroscopic and can absorb moisture from the air, thereby keeping enough water content at the surface to maintain some level of effectiveness. However, the free solubility and low viscosity of the resultant solutions allows the salt to be readily carried off the surface during rainfall.
Other dust control agents have been provided in the art. These agents prevent particulate material from becoming airborne and conventionally function by providing a liquid film that coats and holds particles together. Individual particles become part of an agglomerated collection, which is less likely to take flight due to the increased mass of the collection relative to the individual particles.
Dust control is in most cases a superficial and temporary remediation. Road and/or soil stabilization are more aggressive techniques that involve forming a longer-lasting structure, which incorporates subsurface matter to some depth in combination with an externally applied binder. The binders used for dust control and for road or soil stabilization serve a similar function, with the binding ability or amount of the binder varying across a spectrum.
The art has provided numerous binders that are useful in connection with dust suppression and aggregate (road or soil) stabilization. Known binders for aqueous compositions may be divided roughly into three classes, including lignin sulfonate compounds; chloride salts, specifically calcium chloride or magnesium chloride; and synthetic binders.
For instance, U.S. Pat. No. 6,132,638 to Oldenhove purports to disclose a dust control composition that comprises an anionic surfactant and a dust control agent such as polyvinyl pyrrolidone, a perfluoroalkyl polymer, polysiloxane, and the like.
U.S. Pat. No. 5,860,770 to Hunt purports to disclose a composition for control of soil erosion and dust, the composition containing monomeric resins, enzymes, surfactants and water.
U.S. Pat. Nos. 5,194,174, 3,174,942, and 4,592,931 purport to disclose the use of various synthetic polymers for treating soil.
U.S. Pat. No. 4,001,033 to Anthone, et al. purports to disclose a composition for soil stabilization that includes lignosulfonate with added dispersants such as fatty acid esters and polyoxyethylene ethers. The dispersants are said to improve the distribution of lignin sulfonate. U.S. Pat. Nos. 4,276,077 and 4,387,205 describe a graft modified lignin compound for soil stabilization.
U.S. Pat. Nos. 865,578, 1,075,856, 2,375,019, and 3,053,019 all describe various sulfite waste liquors for soil stabilization.
U.S. Pat. No. 6,065,903 to Doyle purports to disclose the use of tall oil emulsions for soil stabilization to enhance the load bearing characteristics of the soil. An emulsifier is added to allow the insoluble tall oil to form an emulsion in water. U.S. Pat. Nos. 4,437,896 and 4,822,425 purport to describe other tall oil compositions for soil stabilization. Numerous other patents disclose oil based compositions for dust control and/or soil stabilization including U.S. Pat. No. 5,412,007 to Hendrix et al. which is said to disclose a lignosulfonate compound in anionic form as a surfactant for petroleum resins.
Of the current products that provide effective dust suppression, certain drawbacks exist, namely poor longevity, environmental toxicity and cost. Many such products that have a desirable useful life are generally considered to be environmentally unsafe. Other products that are more environmentally friendly have a shorter useful life. Synthetic binders that possess a favorable useful life and that do not have serious environmental problems are available, but such products are costly. Oils and oil emulsions are costly, have stickiness concerns and are not environmentally friendly.
For example, the prior art teaches that lignin compounds are effective for dust control, but only when combined with chloride salts. Due to environmental concerns, there is increasing sensitivity to the use of chloride containing compounds. With respect to chloride compounds, a typical dust control application with a chloride product releases many times more chloride into the environment than does a salt roadway deicing operation. Moreover, known materials derive their effectiveness from the hygroscopicity of one of the components. Although generally effective in drawing enough moisture from the air to immobilize dust particles, the highly soluble nature of the agents causes them to be easily washed away.
It is an object of this invention to provide a dust suppressant composition that is highly effective in reducing the generation of airborne particulate matter and that remains effective for a long period of time. In other embodiments, it is an object to provide a soil stabilization composition.